Fig. 8.
In 1845, Stringfellow, who was now working alone—Henson having abandoned the tests and gone abroad—met with a definite success. He obtained actual flights with a steam-driven model in the form of a monoplane, weighing 8½ lbs. These tests attracted attention among scientists, but they led to nothing else—that is to say, no full-sized machine was the result. But Stringfellow’s model interested many people in the problems of flight. It showed, indeed, although in miniature, that a flying machine could be built and driven through the air; and so this patient experimenter did not labour in vain.
Following Stringfellow, upon the list of those who forged links in the aerial conquest, came Francis Herbert Wenham. His interest in flying, as with many other men, was aroused by watching the birds. Wenham, an engineer by profession, made a voyage up the Nile; and his study of the movement of birds, as they flew near his yacht, caused him to take up aviation in earnest, and carry out experiments for the Aeronautical Society. Wenham was interested largely in the lifting power of planes, and sought efficient shapes. He recommended the building of arched surfaces, so arranged that they had considerable span, but were narrow from front to back; and he suggested also that they should, when fitted to a machine, be placed one above another. Thus Wenham was the inventor of the biplane, as we know that craft to-day.
In explaining this point he wrote:
“Having remarked how thin a stratum of air is displaced between the wings of a bird in rapid flight, it follows that, in order to obtain the necessary length of plane for supporting heavy weights, the surfaces may be superposed, or placed in parallel rows with an interval between them” ([Fig. 9]).
Fig. 9.—Superposed Lifting Planes.
To illustrate his theory, he built a model which had six long, narrow planes, arranged one above the other, rather like the slats of a Venetian blind. Wenham’s experiments were highly important, because they cleared a great deal of ground, and removed many misunderstandings. By showing that a long, narrow plane was more efficient—would, that is to say, carry a greater load through the air than one which was deep from front to back, owing to the fact that it is the front section of an inclined plane that provides the most “lift”; and by illustrating how, in a full-sized machine, such a row of planes could be arranged one above another, Wenham directed men’s thoughts towards a definite goal. By his work, and chiefly by his sifting of data, an outline was obtained of that aeroplane of the future which was actually to fly.
While Wenham was experimenting, an inventor named Penaud, in France, testing a series of models, made one which was driven by the twisting of elastic, and flew quite well. Penaud’s work in this respect is interesting, because small elastic-driven machines, such as he designed, were used afterwards in demonstration, and are flown to-day. For a miniature aeroplane, elastic is an ideal motive force—light and yet providing ample power, and with only one disadvantage: it unwinds itself rapidly, and then the model must descend.